.\"
.\" This file is part of RGBDS.
.\"
.\" Copyright (c) 2010-2019, Anthony J. Bentley and RGBDS contributors.
.\"
.\" SPDX-License-Identifier: MIT
.\"
.Dd November 26, 2019
.Dt RGBLINK 1
.Os
.Sh NAME
.Nm rgblink
.Nd Game Boy linker
.Sh SYNOPSIS
.Nm
.Op Fl dtVvw
.Op Fl l Ar linker_script
.Op Fl m Ar map_file
.Op Fl n Ar sym_file
.Op Fl O Ar overlay_file
.Op Fl o Ar out_file
.Op Fl p Ar pad_value
.Op Fl s Ar symbol
.Ar
.Sh DESCRIPTION
The
.Nm
program links RGB object files, typically created by
.Xr rgbasm 1 ,
into a single Game Boy ROM file.
The format is documented in
.Xr rgbds 5 .
.Pp
ROM0 sections are placed in the first 16 KiB of the output ROM, and ROMX sections are placed in any 16 KiB
.Dq bank
except the first.
If your ROM will only be 32 KiB, you can use the
.Fl t
option to change this.
.Pp
Similarly, WRAM0 sections are placed in the first 4 KiB of WRAM
.Pq Dq bank 0 ,
and WRAMX sections are placed in any bank of the last 4 KiB.
If your ROM doesn't use banked WRAM, you can use the
.Fl w
option to change this.
.Pp
Also, if your ROM is designed for a monochrome Game Boy, you can make sure that you don't use any incompatible section by using the
.Fl d
option, which implies
.Fl w
but also prohibits the use of banked VRAM.
.Pp
Note that options can be abbreviated as long as the abbreviation is unambiguous:
.Fl Fl verb
is
.Fl Fl verbose ,
but
.Fl Fl ver
is invalid because it could also be
.Fl Fl version .
The arguments are as follows:
.Bl -tag -width Ds
.It Fl d , Fl Fl dmg
Enable DMG mode.
Prohibit the use of sections that doesn't exist on a DMG, such as WRAMX and VRAM bank 1.
This option automatically enables
.Fl w .
.It Fl l Ar linker_script, Fl Fl linkerscript Ar linker_script
Specify a linker script file that tells the linker how sections must be placed in the ROM.
The attributes assigned in the linker script must be consistent with any assigned in the code.
See
.Xr rgblink 5
for more information about the linker script format.
.It Fl m Ar map_file , Fl Fl map Ar map_file
Write a map file to the given filename, listing how sections and symbols were assigned.
.It Fl n Ar sym_file , Fl Fl sym Ar sym_file
Write a symbol file to the given filename, listing the address of all exported symbols.
Several external programs can use this information, for example to help debugging ROMs.
.It Fl O Ar overlay_file , Fl Fl overlay Ar overlay_file
If specified, sections will be overlaid "on top" of the provided ROM image.
In that case, all sections must be fixed.
This may be used to patch an existing binary.
.It Fl o Ar out_file , Fl Fl output Ar out_file
Write the ROM image to the given file.
.It Fl p Ar pad_value , Fl Fl pad Ar pad_value
When inserting padding between sections, pad with this value.
Has no effect if
.Fl O
is specified.
The default is 0.
.It Fl s Ar symbol , Fl Fl smart Ar symbol
This option is ignored.
It was supposed to perform smart linking but fell into disrepair, and so has been removed.
It will be reimplemented at some point.
.It Fl t , Fl Fl tiny
Expand the ROM0 section size from 16 KiB to the full 32 KiB assigned to ROM and prohibit the use of ROMX sections.
Useful for ROMs that fit in 32 KiB.
.It Fl V , Fl Fl version
Print the version of the program and exit.
.It Fl v , Fl Fl verbose
Verbose: enable printing more information to standard error.
.It Fl w , Fl Fl wramx
Expand the WRAM0 section size from 4 KiB to the full 8 KiB assigned to WRAM and prohibit the use of WRAMX sections.
.El
.Sh EXAMPLES
All you need for a basic ROM is an object file, which can be made into a ROM image like so:
.Pp
.D1 $ rgblink -o bar.gb foo.o
.Pp
The resulting
.Ar bar.gb
will not have correct checksums (unless you put them in the assembly source).
You should use
.Xr rgbfix 1
to fix these so that the program will actually run in a Game Boy:
.Pp
.Dl $ rgbfix -v bar.gb
.Ed
.Pp
Here is a more complete example:
.Pp
.Dl $ rgblink -o bin/game.gb -n bin/game.sym -p 0xFF obj/title.o obj/engine.o
.Ed
.Sh BUGS
Please report bugs on
.Lk https://github.com/rednex/rgbds/issues GitHub .
.Sh SEE ALSO
.Xr rgbasm 1 ,
.Xr rgblink 5 ,
.Xr rgbfix 1 ,
.Xr rgbds 5 ,
.Xr rgbds 7
.Sh HISTORY
.Nm
was originally written by Carsten S\(/orensen as part of the ASMotor package, and was later packaged in RGBDS by Justin Lloyd.
It is now maintained by a number of contributors at
.Lk https://github.com/rednex/rgbds .
